Reload bonuses are very similar to welcome bonuses. They are usually given at a lower percentage (less than 100%) and to existing customers only. So, for example, a happy hour reload bonus offer might give you 30% on every deposit.
They can also be used to reactivate players who have not been active for a while, or then to reward active players. This is one of the most common ways that casinos reward existing players
Deposit 30€ and play with 60€ this means that when you deposit 30€ the casino will match your deposit.
Deposit 100€ and play with 150€ this means the casino will give you an extra 50€ to play with.
To keep in mind, there is nearly always a wagering requirement on the bonus or then it can be on both, the bonus and the actual deposit.
Reload bonuses and usually offered either at the start of the week or then at the end of the week, it depends per brand and on the Cashback´s, when they are paid.